1. Field of the Invention
The invention relates to a method for operating a video tape recorder which has multiple tracks that are physically in parallel to each other and are collectively accessible as a single logical track, through selectively displaying, in parallel, a plurality of video keyframes, for controlling actual play through selective accessing of a particular displayed keyframe.
2. Description of the Related Art
A method of this kind has been disclosed in U.S. Pat. No. 6,340,971, herein incorporated by reference.
The use of keyframes as representative parts of a video presentation that is recorded for subsequent selective playback has been proposed elsewhere. A video stream may include animation, a series of stills, or an interactive sequence of images. The character of the presentation may be various, such as, film, news, or, for example, a shopping list. State of the art is represented by the article xe2x80x9cContent-Based Video Indexing and Retrievalxe2x80x9d by S. W. Smoliar and H. J. Zhang, IEEE Multimedia, Summer 1994, pages 62-72. In similar manner as playing, the accessing may involve writing, editing, and the like. The parallel character of the physical tracks may be that they run side by side, essentially from the beginning of the tape essentially to its end. Alternatively, the parallelism may be caused in that the tracks run in an oblique manner across the tape, and, therefore, are staggered with respect to each other.
Keyframes may be derived from the video material upon its reception at a user""s premises through some derivation algorithm, or keyframes may be labelled as such by the video provider, for example, in that each new video shot will start with a keyframe. A third assignment mechanism is to separate keyframes by a uniform time interval of play, or by a uniform distance on tape. The present invention recognizes that such keyframes should be utilized so as to give users a dynamic overview over the presentation, combined with useful facilities for enabling them to edit the material in a sensible manner.
Now, the serial stringing of the physical tracks to a single logical track has a complicating effect on the accessibility of the various key-frames, i.e., the time lapse necessary for actual accessing need no longer be proportional to the play time between an actual keyframe and an intended or target keyframe. This may be caused by the fact that each individual physical track may be accessed by quasi-instantaneous cross-track jumping, whereas motion along each physical track needs winding or rewinding the tape. A similar mechanism is present when various different presentations are accessible on the same physical tape in that they are, according to some strategy or another, stored in an interleaved manner. Replay then will need some kind of buffering mechanism that must be loaded to an appropriate degree before actual continuous replay may begin. Now, users may follow all kinds of zapping strategies, but will want to know the incurred delay up to the intended keyframe. This delay should be clear to an inexperienced consumer person, who would usually not be aware of the physical properties and storage format of the tape.
In consequence, among other things, it is an object of the present invention to visually indicate, to an inexperienced user, the actual delay until a particular keyframe may be accessed. As will be discussed hereinafter, the analog indication may be grasped by the user for multiple keyframes displayed side by side. Furthermore, the algorithm for generating the value of the analog indication is straightforward. Advantageously, said analog indication is displayed as framing the associated keyframe. Putting the indication slightly outside the keyframe picture leaves the information contained in the keyframe itself uninfluenced. Advantageously, the analog indication is a color. Colors, in particular, can be seen virtually at a glance. The invention also relates to a video tape recorder arranged for practising the recited method. In this manner, the user gets an apparatus that offers an extremely straightforward manner of accessing even very long video recordings.
The analog quantity may be a color, a grey-scale, a thermometer code, or any appropriate item of which the value is immediately apparent without recourse to decoding one or more digits, character, or the like. The value is generally a static one, because multiple quantities are displayed in parallel, each pertaining to a respective keyframe.
Advantageously, the method is used in association with a tape recorder enhanced with an effectively random access video buffer that is arranged for diminishing the time lapse, while adapting the analog quantity in accordance with the diminishing time lapse. Although, in various instances, the time lapse may be diminished to a substantial degree, the remaining value thereof may warrant its specific display to warn the user that an appreciable time lapse may still be forthcoming.
The invention also relates to a video tape recorder that is arranged for implementing the above method.